How do I prevent Android taking a screenshot when my app goes to the background?

The app I'm currently building has the requirement that the app has to prevent the OS to take a screenshot of the app when it's being pushed into the background for security reasons. This way it won't be able to see the last active screen when switching between apps.

I'm planning to put this functionality in the application class's onPause method, but first I need to find out how I can achieve this functionality.

This definitely secures against manual screenshots and automatic screenshots from the ICS recent-tasks history.

UPDATE: it also secures against Now On Tap or other assistants on Android 6.0; they will not get access to the details of widgets and containers in your UI if the user brings up the assistant.

UPDATE #2: however, not everything in the activity will be protected. Any pop-up windows — Dialog, Spinner, AutoCompleteTextView, action bar overflow, etc. — will be insecure. You can fix the Dialog problem by calling getWindow() on it and setting FLAG_SECURE. The rest... gets tricky. See this blog post for more.